Fix agent loading and categorization issues

- Fixed YAML frontmatter errors in all agent files causing loading failures
- Added proper category fields to all 16 agents for correct classification
- Standardized agent names to match filenames for consistency
- Updated TODO.md to reflect completed agent system fixes
- Enhanced agents-install-cli make target with pip upgrade and user guidance

All agents now load properly without warnings and display in correct categories:
- Documentation (1), Code Quality (4), Project Management (4)
- Development Process (3), Infrastructure (1), Testing (3)

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

agents/agent-test-maintenance.md

@@ -1,3 +1,9 @@
+---
+name: test-maintenance
+description: Specialized agent for analyzing and fixing failing tests in the project
+category: testing
+---
+
 # Test-Fixing Agent
 
 ## Purpose